1. Field of the Invention
The present invention relates to a photoreceptor web steering apparatus for preventing the lateral slip of a photoreceptor web used in a printer, and more particularly, to a photoreceptor web steering apparatus for a printer having an improved structure so that a lateral slip of the photoreceptor web is prevented without tilting the rollers supporting the photoreceptor web.
2. Description of the Related Art
In a printer such as a laser printer, a laser beam scans a photoreceptive medium to form a latent electrostatic image. The latent electrostatic image is developed with a toner of a predetermined color using a development unit and then the developed image is transferred to a printing paper.
Referring to FIG. 1, a general printer has a photoreceptor web 10 circulating around a driving roller 20, a transfer backup roller 30, and a steering roller 41, which are installed in a main body of the printer.
Near the photoreceptor web 10, there is an erasing lamp 60 for erasing a surface electrical potential formed on the photoreceptor web 10 by emitting a light beam, a charger 70 for charging the photoreceptor web 10 from which the surface electrical potential has been removed to a predetermined electrical potential, a plurality of laser scanning units 80 for forming a latent electrostatic image corresponding to each color by scanning the photoreceptor web 10 using a laser beam, and a plurality of development units 90 for developing a portion of the photoreceptor web 10 having the latent electrostatic image.
In a printer having the above structure, since the photoreceptor web 10 is operated while being wound around the respective rollers 20, 30 and 41, a lateral slip of the photoreceptor web 10 in a longitudinal direction of the rollers 20, 30 and 41 is possible.
Thus, the printer includes a lateral slip detecting sensor (not shown) for detecting a lateral slip of the photoreceptor web 10, and a photoreceptor web steering apparatus 40 for correcting the lateral slip.
Referring to FIGS. 1 and 2, a conventional photoreceptor web steering apparatus 40 includes a frame 42 installed at a printer main body 1, a pivot member 46 installed at the frame 42 capable of pivoting, a steering roller 41 installed at the pivot member 46 to support the photoreceptor web 10 to circulate along a predetermined path, a pair of stabilizing rollers 43 installed at the frame 42 to flatten the photoreceptor web 10 passing after the steering roller 41, and an adjusting unit 50 installed at the printer main body 1 to adjust the tilt of the steering roller 41 in upward and downward directions as indicated by arrow "A".
The pivot member 46 is coupled to a pivot bar 44 which is elastically coupled to the frame 42 by a coupling pin 47 so as to be capable of pivoting around a portion where the coupling pin 47 is coupled to a surface of the pivot member 46 in the X-Y plane. The pivot member 46 pivots in a direction to compensate for uneven pressure being applied to a contact portion between the steering roller 41 and the photoreceptor web 10 by an elastic member 45 interposed between the pivot bar 44 and the frame 42. A rotational shaft 41a of the steering roller 41 is coupled to an installation groove 46a formed in the pivot member 46. An elastic piece 48 is installed at the installation groove 46a to support the rotational shaft 41a of the steering roller 41 by pressing the rotational shaft 41a.
The adjusting unit 50 includes a driving motor 53 fixed to a frame 3, the cam member 51 coupled to the rotational shaft 54 of the driving motor 53 and having a cam groove 52, and a pivot guide protrusion 49 coupled to the pivot member 46 and inserted into the cam groove 52. Thus, as the driving motor 53 rotates, the position of the cam groove 52 varies so that the height of the pivot guide protrusion 49 changes. Accordingly, the steering roller 41 pivots around the pivot bar 44 in the directions indicated by arrow "A".
Therefore, when a lateral slip of the photoreceptor web 10 is detected by the lateral-slip detecting sensor, the steering roller 41 is tilted according to the position of the cam member 51. As a result, as the photoreceptor web 10 moves in a latitudinal direction, the lateral slip is corrected.
The respective stabilizing rollers 43 are installed at the frame 42 parallel to the steering roller 41 and contact a portion of the photoreceptor web 10 proceeding toward the steering roller 41 and a portion of the photoreceptor web 10 having passed the steering roller 41 to prevent wrinkles of the photoreceptor web 10. Also, the stabilizing rollers 43 allow the change in height of the photoreceptor web 10 according to the steering so as not to affect the laser scanning unit 80.
However, in the conventional photoreceptor web steering apparatus having the above structure, wrinkles of the photoreceptor web 10 may easily occur since the entire steering apparatus 40 is tilted to correct the lateral slip of the photoreceptor web 10. Thus, since two stabilizing rollers 43 are required and since the distance between the stabilizing rollers 43 and the steering roller 41, "x" in FIG. 1, should be large enough to flatten the wrinkles of the photoreceptor web 10 by the steering roller 41, miniaturization of the printer is limited.
Further, since the elastic member 45 interposed between the pivot bar 44 and the frame 42 applies tension to the photoreceptor web 10, in ensuring the removal of the tensions, the installation structure becomes complicated.